Radiation oncology is a branch of medicine that uses various types of radiation to treat and control cancer. Linear accelerators (LINACS) are used to deliver radiation to the patent for treatment. The radiation is typically in the form of X-rays and Gamma rays. X-rays and Gamma rays are high frequency ionizing light energy which has very short wavelengths. As the rays pass through matter they may lose energy or intensity by stripping the electrons off the atoms of the matter.
This ionizing of matter may destroy the DNA of cells. This is particularly effective against cancerous cells since, unlike healthy cells, they cannot easily repair damaged to their DNA. This results in the death of cancerous cells. Healthy tissue subjected to the same intensity of radiation as the cancerous cells can also die causing unwanted side effects.
To reduce the damage to healthy tissue, intensity modulated radiation therapy (IMRT) was developed with 3-D conformal radiation therapy. IMRT results in a “shaped” and “sculpted” beam which maximizes dose delivery to the cancerous tissue while minimizing dose delivery to the surrounding healthy tissue. By treating the tumor with controlled doses from multiple angles, total dose delivered to the cancerous tissue is equivalent to conventional treatment.
Compensator based IMRT uses a compensator mounted in the head of the LINAC to “sculpt” the beam and a block, if used, separately mounted below the compensator to “shape” the beam (see prior art FIG. 3).
The compensators and blocks are typically made out of high density material. The higher the density of the material, the more chance the radiation beam has to interact with the atoms of that material and lose energy or intensity as the beam passes through.
The beam emitted from the LINAC, before the compensator, is typically conical in shape. By using a block made out of a high density material with a cutout in the shape of the tumor in or around the middle of the block, the beam can be “shaped” by blocking the beam outside the tumor and allowing the full intensity of the beam in the two dimensional shape of the tumor to pass through. These blocks are typically molded out of a lead based alloy called Cerrobend® and are typically 2 to 3 inches thick when used with compensators.
The compensator and the block (if used) are typically aligned with the central axis of the radiation beam and the compensator lines up with the cutout in the block and modulates the intensity of the beam. The compensator is typically milled out of brass, aluminum, bronze, tungsten, Cerrobend®, other suitable material depending on the initial intensity of the beam and “sculpts” the beam by having little material thickness where the beam has line of sight to the tumor and more material where the beam lines up with healthy tissue and critical structures of the body (see prior art FIGS. 4 and 4A).
Each patient is treated typically with 3 to 11 differently shaped compensators and typically their corresponding blocks. Even though this style of treatment is very effective for the patient, there are several drawbacks for the centers administering the care.                1. The biggest drawback for the center is handling and working with a hazardous material such as the Cerrobend. Special rooms and ventilation systems are required to protect the health of the employees and to prevent any lead dust from escaping the block room and contaminating the rest of the hospital.        2. The center must have a trained and experienced block maker on staff.        3. Special trays are required to mount the blocks on. These trays are typically made out of Acrylic and degrade with time due to radiation exposure. This causes the material to become brittle and dangerous for use around patients.        4. Each block must be matched up with the correct compensator for treatment or the patient may be harmed. This is made more difficult due to the fact that for each angle the patient is treated from, a different compensator and block is required. These are changed out “on the fly” during each treatment.        5. The block must align correctly with the rest of the system or the patient may be mistreated. This depends upon the tolerances of the adaptor, tolerances of the block tray, and the competency of the block maker.        
Some centers have opted to get rid of the separate blocks by, typically, doing one of two things.                A. The center uses an extremely high density material, such as cast Cerrobend or tungsten powder, to create a combination block and compensator. These devices successfully act as beam shapers to substantially reduce dose to surrounding healthy tissue, but the relatively high density of the material magnifies any error in the modulation of the beam due to manufacturing tolerances, voids and shrinkage which is inherent to the casting process, and shifting of the powder.        B. Due to the drawbacks associated with using high density material to create a combination block and compensator, many centers that have opted to eliminate separate beam shaping blocks during treatment have selected materials commonly used for compensators which have good beam modulating or “sculpting” characteristics, typically brass and aluminum. These materials are less dense than materials used specifically for beam blocking and therefore do not magnify errors due to manufacturing tolerances as much as the higher density materials do. This results in a more accurate dose being delivered to the tumor. Unfortunately, the lower density of the material allows a high dose to be delivered to the surrounding tissue than would normally have occurred if separate, high density blocks were used.        
A radiation oncologist and physicist prepare a treatment plan, specifically for the specific patient. The plan includes restraints for radiation exposure for critical structure as well as restraints or a prescription for radiation of the tumor area. From these parameters, a specific treatment plan for the patient is prepared. These parameters are sent to a manufacturer for preparing, in ways known in the art, the compensator and block, if used, that will provide the plan parameters for the LINAC machine used.
Radiation is initially projected by the LINAC head in a multiplicity of pencil beams directed generally towards the tumor target area (such as a cancerous organ) on a patient. The beam, after initial projection, is subsequently modified by the conventional processes of shaping and sculpting. Generally, shaping is the process of defining an external boundary or a through profile that will cover the profile (projected outline) of a target tumor as projected downstream from the various shaping mechanisms. The shaping mechanisms are typically jaws (LJ) upstream of the conventional compensator and a conventional block, CB, for example, comprising Cerrobend®, separate from and mounted downstream of a conventional compensator.
IMRT typically modulates (sculpts) the intensity of the radiation that falls within the through profile by means known in the art, typically, machining a compensator into an inverse contour represented by the tissue variation dictating by target dosage.
As illustrated in FIGS. 3, 4 and 4A, the material compositions of the conventional compensator and Cerrobend block are usually different (typically, the block has a material of greater density), but they are also shaped differently, dictated by their differing functions. Ideally, if used, the block has a profile shaping function and the compensator acts to modify or sculpt, as by modulation, the intensity of the radiation passing through the compensator profile. Moreover, while gross beam shaping or blocking is provided upstream of the conventional compensator by jaws LJ, the shaping is refined by a conventional block (if used) mounted downstream of a separate conventional compensator as illustrated in FIG. 3.
Typically, conventional compensators mount on a conventional compensator tray (CCT) as by conventional fasteners engaging a flange on the conventional compensator and the tray. Conventional compensator tray (CCT) has a pair of spaced apart ridges for engagement with upper slots (US) in the accessory adapter (AA) of a typical LINAC machine.
Similarly, a conventional block (CB) may be mounted by fasteners or in other ways known in the trade to a conventional block tray (CBT) which, as with the conventional compensator tray (CCT), has ridges spaced apart for joining lower slots (LS) on an accessory adaptor (AA) of the typical LINAC machine for engagement with a wedge tray slot.
Thus, typically the conventional compensator and conventional block are handled separately and are positioned vis-à-vis one to the other through careful placement on trays and careful placement of the trays in the accessory adapter (AA) of the LINAC machine (LM).